I don't have an RCD510 or even a mk6, but currently there is no way to get the iphone interface onto any type of screen by default.
I have been looking for an RCA cable for my iphone (most aren't compatible with the 3GS atm) which combined with the iphone jailbreak will allow me to show my iphones screen on the head units display. There is a jailbreak app that lets you change the TV out settings to display anything. I think that this is the only way possible at the moment, and I don't know if the RCD510 has a composite video input?